1980s Messenger (WH Smith) cap repair

[kyelani]

Hello,

 

the brass (?) cap of my treasured second ever fountain pen (my second school pen) has sustained a hairline crack in its acrylic (?) covering. I’d love to prevent it from getting any worse and I’m trying to remove the clip screw, with no luck so far. 
 

it was friction fit to a point and I’ve managed to release the clip, but the screw won’t come all the way out, which means I can’t risk a repair on the crack. 
 

While I’m waiting for delivery of an endoscope, does anyone happen to know if the inner cap is what’s preventing the screw from being released? They do seem to turn together when I rotate the screw, but there’s no thread that I can see or feel. The radial channels that are visible on the plastic attached to the screw aren’t a thread, either. 
 

 

[kyelani]

After looking inside the cap with an endoscope I now know that the semi-transparent plastic part that’s attached to the screw is definitely part of the inner cap. 
 

That being the case, it seems I need to somehow extricate the screw from the exposed plastic before I can assess what’s possible in terms of fixing the crack. 
 

If anyone has any best advice for me about separating the two parts without doing any damage I’d be extremely grateful. 

[kyelani]

In case this is of interest or help to someone in the future, I managed to separate the screw by painstakingly rotating the cap and levering it with my thumbnail, without putting any pressure on the top of the crack in the cap. The screw actually came out quite easily after three very slow and careful revolutions and I’ve now got a clear view of the crack in the cap. 
 

The acrylic “wrap” around the brass extends above it by about 5mm, so that part’s presumably quite fragile and I’ll need now to research the best way to apply a stabilising fix to the crack that doesn’t spoil the otherwise lovely condition of this pen, and what materials to use.